Análisis paramétrico para el doblado de chapa con herramientas impresas mediante FDM

Abstract

[ES] Este trabajo se realiza con el objetivo de buscar una alternativa al doblado de chapa convencional mediante matrices metálicas, que para producciones pequeñas o de piezas personalizadas resulta bastante costoso. La alternativa planteada será utilizar polímeros, centrándose en la impresión FDM para la realización del utillaje de doblado. Para demostrar que esta hipótesis se puede cumplir se comienza diseñando el utillaje de doblado. Para ello es necesario conocer la pieza que se va a doblar. Una vez diseñado el utillaje, es necesario comprobar que su funcionamiento es correcto y realiza bien el doblado deseado. En dichas comprobaciones se realizan varias modificaciones hasta que se da con el diseño correcto para obtener la pieza de doblado elegida. Debido a que en la impresión FDM hay tanta variedad de parámetros que se pueden elegir para la impresión, es necesario realizar un análisis paramétrico mediante un modelo de diseño de experimentos factorial (DoE). Las probetas elegidas para este análisis se basan en la norma de ISO 604 (Plásticos. Determinación de las propiedades en compresión). Las probetas se imprimen con la configuración deseada y se ensayan a tracción, obteniendo como resultado la fuerza máxima (kN) que soporta cada probeta. Una vez analizados los resultados, el utillaje se imprime con la mejor configuración Finalmente, el utillaje se pone a prueba doblando 50 chapas de acero S275 de 0,8 mm de espesor. Posteriormente, se analizan lo dobleces de las chapas comprobándose que el doblado se efectúa de forma correcta, llegando a la forma deseada en la chapa. Resultado muy satisfactorio ya que era el objetivo principal. Por otro lado, se realiza un análisis de impacto económico comparando un utillaje convencional con el expuesto en el trabajo, llegando a la conclusión de que la diferencia en el importe total de fabricación es del 97,75% en favor del polímero. Para un lote pequeño de 50 piezas supondría un coste unitario de 3,32€ en plástico y 147,30€ en metal. Para llegar a ese importe tan económico en plástico serían necesarias realizar 2.200 piezas en metal.

[EN] This work is carried out with the aim of finding an alternative to conventional sheet metal bending using metal dies, which is quite costly mainly for small productions or customised parts. The alternative proposed will be to use polymers, focusing on FDM printing for the realisation of the bending tooling. In order to demonstrate that this hypothesis can be fulfilled, it is first necessary to design the bending tooling that will be needed. To do this, it is necessary to know the part to be bent, which in this case will be a U-bend with two sharper bends. Once the tooling has been designed, it is necessary to print it in order to check that it works correctly and performs the desired bend. During these checks, several modifications are made until the correct design is found to obtain the bent part of choice. Because there is such a wide variety of parameters that can be chosen for printing in FDM printing, it is necessary to perform a parametric analysis using a factorial design of experiments model. Once the parameters of interest have been chosen, the analysis reports all possible combinations between them. These will each be associated with a test specimen. The design of these test specimens will be carried out on the basis of the standard "Plastics. Determination of properties in compression" (ISO 604) and through the design software associated with the printer, each configuration will be associated. Once all the configurations have been printed, compression tests are carried out using a ME-402 testing machine, giving as a result the maximum force (kN) that each specimen can withstand. Subsequently, the necessary modifications are made to the design of the polymeric tooling and it is printed again, associating it with a configuration of printing parameters obtained from the compression tests that is strong enough to bend the chosen steel sheets. Finally, the bending tests are completed using the printed tooling. After several tests, it is necessary to make the last modification to the design, specifically to the punch. Once modified, the tests continued, and it was found that the bending was carried out without modifying the plastic tooling and reaching the desired shape in the sheet. The result was very satisfactory, as this was the main objective. In addition, an economic impact analysis is carried out, as one of the objectives of the work was to find an alternative for bending in order to reduce costs. A comparison of the production of the tooling in steel and in polymer was carried out, reaching the conclusion that the difference in the total manufacturing cost is 97.75% in favour of polymer. For example, for a small batch of 50 pieces, a unit would cost €3.32 to make in plastic and €147.30 in metal. To reach such a low cost in plastic, 2,200 pieces would need to be made in metal.